Most companies fail, making their stock options worthless. And even the few companies that succeed usually hit bumps in the road that dilute the stock options or put their value underwater.

So if you have a reason to think your idea of "substantial equity" is much more likely than average to ever be worth anything at all, you should make that fact a key part of your pitch. (Or if you're indifferent between equity and salary, offer more salary and less equity.)

Unless your company ends up being the next Google or Facebook (which is a statistically unlikely outcome for any startup), your "substantial equity" may never be worth any significant amount of money. Living in NYC is expensive, and you can't pay your rent with stock options.

I only have anecdotal data, I don't think many people have more, but I am very sure a decent senior dev can get way more than what you are offering.

I think there is more to a job than just the salary, but at least be open about the fact that there are open positions doing similar work in the same city offering significantly more.